Magnetic snap switch



Aug. 30, 1960 H. c. ovsHxNsKY MAGNETIC SNAP swITcH Filed Feb. 24. 195s INVENTOR. /ererz if @Vs/insign BY 7 a United States Patent O 2,951,135 MAGNETIC SNAP SWITCH Herbert Ovshinsky, Oak Park, Mich., assignor to Tann Corporation, Detroit, Mich., a corporation of Michigan Filed Feb. 24, 1958, Ser. No. 717,119 7 Claims. (Cl. 200-87) This invention relates to an improved magnetically actuated device, and more particularly to an improved magnet arrangement for actuating an element of a device to advanced and retracted positions.

The device of the present invention has many applications and only by way of example is the device herein illustrated as being employed in combination with an4 electric switch. The switch `as herein illustrated is of the plunger actuated type especially suited for use as a proximity, or limit switch. The device is exceedingly simple, requiring no mechanical linkage between the plunger and the electrical contacting elements. The improved magnetic linkage of the present invention transmits energy from the reciprocal or ro-tatable plunger to a rotor for opening and closing the switch contacts. Permanent magnets are used for the magnetic linkage of a type to produce high eiciency and positive force transmission.

The electrical contacting arrangement in the switch may be similar in principle to the arrangement in the magnetic switches shown in the copending applications of Stanford R. Ovshinsky, Serial No. 644,393, filed March 6, 1957; Serial No. 644,360, tiled March 6, 1957; Serial No. 645,260, led March 11, 1957, and Serial No. 644,228, filed March 6, 1957, in that a plurality of loosely held electrically conductive magnetizable balls are. magnetically aligned when the switch is closed to form a conducting path between a pair of electrodes. The balls are made of a magnetizable material and link themselves together in chain-like arrangements connecting the two contacts when they are brought into a magnetic field therebetween. When the magnetic eld is removed, the balls fall away from the contacts, thus breaking the circuit.

In the present invention, the balls are carried in an insulating rotor, which selectively carries them into and out of `a magnetic eld formed by a pair of magnets situated one above and one beneath the horizontally disposed rotor. These magnets in the illustrated embodiment of the invention also serve as the switch contacts to which the external circuit is connected.

According to a further feature of the invention, high conductivity and low conductivity balls are separately confined in adjacent portions of the rotor chamber, the low conductivity balls being the first to engage the electrodes tomake the circuit :and being the last to be disengaged to break the circuit, thus reducing electrical surges and arcing.

The angular position of the rotor is controlled by coaxially arranged magnets carried by the rotor and the plunger. These magnets are arranged :and polarized to control the `angular position of the rotor with respect to the plunger, and effect angular oscillation of the rotor in response to longitudinal reciprocation of the plunger.

Accordingly, the principal objects of the invention are: to provide an improved magnetically actuated proximity, or limit` switch; to provide an improved magnetic linkage ice for converting translational movement of an actuating element into a rotational force to rotate a rotatable element; to provide an improved magnetic linkage arrangement for making electrical contact between a pair of electrodes in an electrical switch; to provide an improved magnetic linkage for developing an angular force in response to relative translational movement between a pair of members; to provide an improved electrical switch in which a relatively high resistance contact is established between a pair of electrodes when the switch is partially closed, and a low resistance contact is established when the switch is fully closed; `and n general to provide a limit switch which is simple in construction,

, positive in operation and economical of manufacture.

Other objects and features of novelty of the invention will be specically pointed out, or will otherwise become apparent when referring for a better understanding of the invention to the following description, taken in conjunction with the accompanying drawing, wherein:

Figure l is an elevational view of a limit switch according to a preferred embodiment of the present invention;

Fig. 2 is a cross-sectional view of the limit switch illustrated in Fig. l, taken generally along the section line 2-2 thereof;

Fig. 3 is a horizontal sectional view of the switch as shown in Fig. 2, taken generally along the section line 3-3 thereof;

Fig. 4 is a horizontal sectional View of the limit switch as shown in Fig. 2, taken generally along the section line 4 4 thereof;

Fig. 5 is a horizontal sectional view of the limit Switch as shown in Fig. 2, taken generally along the section line 5 5 thereof; and

Fig. 6 is a perspective view of the rotor magnet of the switch shown in the preceding gures, showing the magnet apart from the switch.

Referring now to the drawing, a double throw limit switch which is shown by way of example includes an insulating rotor 10 iixed upon -a shaft 12, which is journaled in an insulating central frame member 14. This frame member 14 is mounted within a casing 16 and the various electrical elements of the switch are mounted upon it, including leads 18 and 20 to which the binding posts 21 are attached for connectton to an external circuit. The leads 18 and 20 are conductively attached to upper and lower permanent magnet electrodes 22 and 24 which are mounted in pairs within apertures (not separately designated) in the frame member 14, one electrode 22 of each pair above and one below the rotor 10. The electrodes 22 and 2,4 of each pair are 'aligned with each other, and are spaced apart sutiiciently to allow adequate clearance for rotation of the rotor 10 between them. These parmanent magnet electrodes 22 and 24 are axially polarized in the same direction so that a continuous magnetic held is established between them.

The rotor 10 is mounted for rotation within the frame member 14 and is provided with an off-center chamber, or aperture 26, which is closed at both ends by the frame member 14, and in which a number of electrically conductive magnetic yballs 28 are loosely conned. When the aperture 26 is between either pair of the magnetic electrodes 22 land 24, the balls are magnet-ized and aligned with the magnetic eld, being formed into a chainalike configuration and making electrical contact between the pai-r of electrodes, as illustrated in Fig. 2. The contact is broken whenever the rotor is moved to carry the balls 28 away from the electrode pair. In the illustrated embodiment, the two pairs of electrodes 22 and 24 are arranged to be alternately contacted by the balls 28, the rotor 10 having two operative positions,

making contact between one pair of electrodes in its first position and between the other pair of electrodes when it is in its second position.

'Ihe rotor 10 also carries an abutment stop l3l) for limiting its rotational travel in yboth directions by striking against the ci-rcumferentially facing edges of the frame member i4. l

In the present embodiment, the aperture 26 is preferably divided into a central portion 32 `and two side portions 34, as best shown in Fig. 3, and 'the balls 28 in the side portions 34 are of relatively low conductivity so that the initial contact made between 'the electrodes is a relatively high resistance contact. the central portion 32 of the aperture are of relatively high conductivity, sov that the inal contact established when-the switch is fully closed is a relatively low resistance contact. in action Vto a rheos-tat to minimize 'electrical surges and -arcing during making and breaking of lthe contacts, the high resistance balls 28 being the first to make and the last to break contact when the switch is actuated.

The effect of this arrangement is similar` The balls 28 in Y Rotation of the rotor iii responsively to translational.

movement of the plunger 36 -is veffected by a` magnetic coupling arrangement. magnet 38 is mounted on the rotor shaft 28 for rotation therewith, and a relativelyshort magnet 42 of generally similar shape is positioned around the rotor magnet and mounted for movement with the plunger 36. The rotor magnet 38 is magnetized in a checker-board pattern, and has two tiers 39 and 4d of alternate north and south A specially polarized toroidal` poles on its outer surface, the north and south poles of the uper t-ier 39 being offset 90 from the corresponding north and south poles of the lower tier 40. The plunger magnet 42 is also magnetized with alternate quadrants of opposite polarity, but with only a single tier of alternate north and south poles on its inner surface, and its length is approximately equal to the length of each one of the tiers of the rotor magnet. The rotor magnet 3S tends to align itself in one angular position relative to theV magnet and carrier upwardly. 'Ilhe carrier 44 is preferably made of a non-magnetic, or lo-w permeability material in order to direct the magnetic eld of the plunger magnet 42 in a radial direction and thus tot maximize the force developed between the plunger magnet 42 and the rotor magnet 38.

When the plunger 36 is extended, the plunger magnet 42 is adjacent to the upper tier 39 of the rotor ymagnet, the rotor 10 is urged .ina clockwise direction as viewed in Fig. 3, and the ball-containing aperture 26 is positioned between the normally closed pair of electrodes `22 and 24. The limit stop 30 is preferably adjusted so that the rotor magnet 38 cannot align itself fully with .the plunger magnet 42, in order to maintain a constant biasing force on the rotor and to avoid overcenter operation of the magnets. When the plunger 36 is depressed to actuate the switch, the plunger magnet 42 is moved adjacent to the lower tier 40, which then tends to align itself with the plunger magnet 42, and drives the rotor 10 counterclockwise, as viewed in Fig. 3, moving the aperture 26 from the normally closed electrodes to the normally open electrodes. When the plunger is released, it is returned to its extended position by the biasing spring 46, and the rotor 10 is positively driven in the return direction by the interaction of the plunger magnet 42 with the upper tier 3910i therotor magnet.

For maximum resistance to demagnetization through `aging and by mechanical impacts and the like, and for minimum cost in construct-ing the switch, it is preferred to make the actuating magnets 38 and 42 of a ferrite material having a relativelyhighcoercivity, such as, for example, Indox (Indiana Steel Products Co.) which is the heat reaction product of barium oxide and iron oxide in a mol. ratio of one barium oxide 'to approximately six ferrie oxide. This material has a high coercivity and may be magnetized in thin `sections without danger of self-demagnetization or loss of ilux by mechanical shocks.

The magnetic electrodes 22 `and 24 may be made of an electrically conductive magnetic material suc'h as Alnioo V, and the balls '23 may be made of any electrically conductive, relatively soft magnetic material, such as, for example, soft iron, or an alloy of iron and nickel,

preferably having a relatively loW coerciv-ity. The llow v conductivity balls 28 inthe side, or makeand-break`r portions 34 `of the rotor aperture are preferably of 'low' electrical conductivity and may be of solid Iironor of an such as silver in order to minimize the contact 'resistance of the switch when it is in a fully closed position.

rIlhus an operating element is provided not only for a switch lbut for any device requiring a quick advance yand return movement.

rotation of the roto-r lo could return the rotor if an additional magnetic section, similar to the iirst section 39, were added below the section 40. The rotor may be revolved to cause the plunger to be longitudinally moved by the flux of the magnets due to the force in attraction or repulsion therebetween as described above.

What is claimed: 1. In a work performing device, spaced contacts, a

rotor having -contact bridging means thereon, a plunger-` mounted for longitudinal movement relative to said rotor, and magnetic means for coupling said plunger to said rotor and for developing a force tending to rotate said rotor in response to said translational movement of said plunger for advancing said bridging means between said contacts.

2. In a work performing device, spaced contacts, a

rotor having contact bridging means thereon, a plunger mounted for longitudinal movement normal to the plane of rotation of said rotor, a iirst magnet mounted on said rotor for rotation therewith, a second magnet mounted adjacent to said rst magnet and carried by said plunger, V

a plurality of spaced portions of each one of said magnets being magnetized in different directions so that movement of said plunger changes the angular magnetic forces between said magnets to thereby rotate said rotor and advance said contact bridging means into engagement Y with said spaced contacts.

3. ln a work performing device, a rotor, a plunger mounted tor longitudinal movement normal to theplane f of rotation of said rotor, a rst magnet mounted on said rotor for rotation therewith, a second magnet mounted adjacent to said rst magnet and carried by said plunger, said magnets being in telescoped relation and having spaced portions magnetized in different directions so that the angular movement of the rotor moves the plunger longitudinally.

4. In a work performing device, a rotor, a plunger mounted formovement normal to the plane of lrotation of said rotor, a iirst magnet mounted on said rotor for rotation therewith, a second magnet mounted adjacent to said first magnet on said plunger for movement therelt is to be understood that a snap' return action occurs when the plunger is released and returns to its initial position and that a further movementl of the plunger beyond its initial movement and the with, said magnets being coaxially aligned one Within the other and having angularly spaced portions of opposite magnetic polarity, the poles of one of said magnets being arranged in two tiers angularly offset from each other whereby said first magnet tends to align itself in one of two different angular positions relative to said second magnet depending on the relative axial positions of said magnets.

5. In a work performing device, a rotor, a plunger mounted for reciprocation normal to the plane of rotation of said rotor, a first magnet mounted on said rotor for rotation therewith, a second magnet mounted on said plunger adjacent to said first magnet for movement-with said plunger, said magnets being coaxially aligned one within the other and being of different lengths, both of said magnets having angularly spaced quadrant portions of opposite magnetic polarity, the poles of the longer one of said magnets being larranged in two tiers offset 90 from each other whereby said magnets are locked in position or moved to a second position with a fast action by the force of said magnets.

6. In a work performing device, a rotor, a plunger mounted for movement normal to the plane of rotation of said rotor, a iirst magnet mounted on said rotor for rotation therewith, a second magnet mounted on said plunger adjacent to said first magnet for movement with said plunger, said first magnet being of generally cylindrical shape and having adjacent quadrant portions of opposite magnetic polarity, the arrangement at one end of said magnet being offset 90 from the arrangement at the opposite end thereof, said second magnet being also of cylindrical shape and of about one-half the length of said first magnet and being iitted closely around said iirst magnet, said second magnet having adjacent quadrant portions of opposite magnetic polarity on its inner 6 surface, said first magnet tending to align itself in one angular position relative to said second magnet when said second magnet is adjacent to said one end of said first magnet and to align itself in a different angular position when said second magnet is adjacent to said Iopposite end.

7. In a work performing device, a pair of eltrodes, means for establishing a magnetic eld between said electrodes, a rotor mounted for rotation through said field and defining a chamber open at both ends, the ends of said chamber being closable by said electrodes when said rotor is in one angular position, means for closing the ends of said chamber when said rotor is away from said one position, a plurality of electrically conductive magnetic balls confined in said chamber and eiective responsively to said magnetic iield to establish an electrically conductive path between said electrodes when said rotor is in said one position, a plunger mounted for reciprocating translational movement relative to said rotor, a first magnet mounted for rotation with said rotor, and a second magnet mounted on said plunger adjacent to said first magnet for movement with said plunger, said magnets being polarized so that said rotor is magnetically urged toward said one angular position when said plunger is at one end of its travel and is urged away from said one angular position when said plunger is at the opposite end of its travel.

References Cited in the le of this patent UNITED STATES PATENTS 2,015,156 Richmond Sept. 24, 1935 2,102,409 Falls Dec. 14, 1937 2,521,723 Hubbell Sept. 12, 1950 2,827,531 OBrien Mar. 18, 1958 2,853,576 Tigerschold Sept. 23, 1958 

